Once efforts to limit absorption have been undertaken, the focus shifts to enhancing elimination. The exclusive elimination of lithium via the kidneys forms the cornerstone of treatment. Most patients can be managed conservatively with intravenous (IV) normal saline, which provides a sodium load in addition to hydration. If hyponatremia is present, the body retains sodium, resulting in lithium reabsorption. Maintaining sodium at the upper limit of normal is essential to ensure adequate elimination. Kidney function and urine output should be monitored, along with lithium levels, to confirm a continued downtrend.
In cases of severe toxicity, hemodialysis may be required for lithium removal. Properties of lithium that make it amenable to dialysis include low molecular weight, low volume of distribution, and low protein binding. Hemodialysis can increase the clearance of lithium four- to tenfold. Expert consensus guidelines from the Extracorporeal Treatments in Poisoning (EXTRIP) Workgroup recommend dialysis when kidney function is impaired and the lithium level is > 4 mEq/L or when mental status changes, seizures, or life-threatening arrhythmias are present, regardless of the lithium level. Other considerations include a lithium level > 5 mEq/L, the presence of significant confusion, or if the time expected to reduce the lithium level to < 1 mEq/L is more than 36 hours.
Dialysis should continue until the lithium level is < 1 mEq/L or clinical improvement is noted. Intermittent hemodialysis is the preferred method for removal. If hemodialysis is unavailable, continuous renal replacement therapy is an alternative, but it is approximately three times less efficient than hemodialysis.[20,21,22] After dialysis, a rebound effect may occur, either from continued GI absorption or from redistribution of lithium out of the tissues into the blood compartment. Symptoms may return during rebound, and redistribution into the tissues will occur if lithium is not removed.
The patient in this case was given indomethacin 50 mg orally every 8 hours. This resulted in an increase in urine osmolality within hours of administration. Hydration was continued with IV normal saline, and the sodium level was kept within the higher range of normal to facilitate lithium excretion. Over the next 3 days, lithium levels trended down into the therapeutic range, and the patient's mental status, tremor, and ataxia gradually improved. In discussions with the psychiatry service, it was decided that the benefits of maintaining the patient on lithium for mood stabilization outweighed the risks for future episodes of chronic toxicity.
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